I went with the Shadowbox JS plugin. There wasn’t really anything in the settings that I needed to modify.

I put a link around the whole box….primarily because my case called for it to work more as a button than a “read more”. So I added <a href="<?php the_permalink() ?>" rel="shadowbox"> to the archives template but basically you’d end up putting rel=”shadowbox” wherever you’d like it to display as a lightbox/pop-up.